1. Field of the Invention
This invention relates generally to methods and apparatuses for applying elastic segments to a base material. More particularly, it concerns the application of elastic segments to a base material in a direction which is transverse to the direction in which the base material is being moved in a production line.
2. Description of the Prior Art
There are a great number of methods and apparatus disclosed in the prior art for applying segments of elastic to a base material. Particularly in the field of disposable garments such as baby diapers and incontinence pads, where production methods must be extremely efficient and economical, there have been several attempts to simplify and speed up the process. Most of these methods are limited to applying the elastic in the same direction as the base material is moving in the production line. For examples, see U.S. Pat. Nos. 4,239,578; 4,297,157; 4,309,236; 4,353,762; 4,360,398; 4,364,787; and 4,371,417. In each of these designs, a strip of elastic is brought in contact with the base material and then be various arrangements of drums and rollers the elastic is attached as the base material moves past, thereby fixing the elastic in the direction the base material is moving.
There exists a need, however, for an efficient method and apparatus to apply elastic segments in a direction transverse to that of the production line. For example, certain garments, such as diapers and incontinence pads, are constructed with elastic segments running in two directions, i.e. for the leg portions and the waist portion. In this example, unless one set of elastic segments is applied followed by a 90.degree. rotation of the garment before applying the second set, a transverse applying design is required. In addition, there may be other factors such as product dimensions and process parameters which make a transverse application desirable.
U.S. Pat. Nos. 3,828,367 and 4,293,367 both describe processes for applying elastic to a moving base material wherein the elastic strip is moved transversely to apply a non-linear elastic segment to the base material. Although these designs are beneficial for some applications, because they both use the travel of the base material to apply the elastic, neither would be suitable for the applications mentioned above.
U.S. Pat. No. 4,240,866, directed to an apparatus, and U.S. Pat. No. 4,285,747 directed to a corresponding method, teach a process for applying elastic segments transverse to the production line travel. The disclosed apparatus is similar to those mentioned above in that it applies the elastic from a roller onto the base material as it passes by. The difference is that short elastic segments are transversely cut from a wide roll of elastic thereby producing a strip which is wide enough to extend across the intended area of application. These wide segments are rotated on an equally wide drum and brought into contact with the moving sheet of base material.
U.S. Pat. No. 4,284,454 also discloses a method for applying elastic segments transversely to a moving base material in manufacturing diapers. This relatively complex apparatus includes a set of cam or piston operated grippers, mounted on an endless chain moving transverse to the production line, which stretch the elastic and move it across the base material. A second set of grippers, mounted on an endless chain moving with the production line, pick up the stretched piece of elastic, apply it to the base material and hold it in place until the remaining layers of the diaper are assembled.